Question

a sudden event that causes many people to suffer

Answer 1

A sudden event that causes many people to suffer may be referred to earthquake.

An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves.

It takes away million of people's lives. Many houses get shattered due to earthquake. It is prone in those areas where plates tectonic movements are highly active.

Answer 2

A sudden event that cause people to suffer is catastrophe.

It can be touted as natural disaster. It can be of many types such as an act of god, calamity, disaster, violence, catastrophe, apocalypse, geohazard, or any other such thing.

This brings a lot of damage and make people suffer in various means. It can also be fatal at times.